Just because a street is one way does not mean it is so narrow that only one vehicle can fit through. Streets may be one way because it discourages unnecessary

Just because a street is one way does not mean it is so narrow that only one vehicle can fit through. Streets may be one way because it discourages unnecessary automotive traffic and it allows the rest of the space to be dedicated to bicyclist or use for residential and commercial purposes (outdoor seating, space for games, etc). So even if the streets are one way, there will often be space for the ambulance to maneuver around blocked vehicles. And if there's not, the ambulance can take another street or road. If it's the only route that can access that location, then with any sane amount of urban planning then the ambulance will be within a short walking distance to the location (and more often than not within eyesight).